My final-year physics project at the University of Liverpool, supervised by Prof Robert Page and Prof David Joss: a recoil-decay tagged γ-γ coincidence spectroscopy study of 175Au. 175Au sits below the Z = 82 shell closure, where near-spherical hole configurations compete with deformation-driving intruder excitations, a textbook setting for shape coexistence. Using recoil-decay tagged data from the JUROGAM + RITU + GREAT setup at the University of Jyväskylä Accelerator Laboratory, I built an updated level scheme (including 30 previously unpublished weak linking transitions), used rotational diagnostics to argue for distinct intrinsic deformations across the observed bands, and built a reproducible coincidence-analysis workflow with a machine-learning parameter-selection stage for a deterministic coincidence interpreter.

Band 5 of the 175Au level scheme, a negative-parity strongly coupled structure with interleaved M1/E2 transitions decaying into the 11/2- anchor
Figure. Band 5 of the working level scheme: a negative-parity, strongly coupled structure with interleaved M1/E2 transitions feeding the 11/2− anchor.

What's in the report

The full report covers the nuclear-structure background (liquid-drop and Nilsson models, rotational coupling schemes, signature and staggering, Harris plots), the experimental setup (JUROGAM's HPGe array, the RITU gas-filled recoil separator, and the GREAT focal-plane spectrometer), the coincidence-gating analysis workflow in Radware, the resulting level scheme and band-by-band interpretation for 175Au, and the machine-learning assisted coincidence interpreter built to speed up peak-finding and cascade-seeding on future datasets. It closes with systematics comparisons against neighbouring Au, Hg, and Pt isotopes, and full appendices covering the level-scheme validation checks, the angular-momentum coupling logic behind the band assignments, and supplementary figures.

This was an assessed university report, not something written for public distribution, so I'm keeping the PDF behind a password. Happy to share it directly if you'd like to read it.

Symmetric projection spectrum with smoothed baseline (top) and residual peaks detected by the coincidence interpreter (bottom)
Figure. Output of the machine-learning assisted coincidence interpreter's peak-finding stage on the 175Au coincidence matrix: smoothed projection and baseline (top), residual with detected peaks (bottom).

Read the report